Among those constant velocity universal joints that are used for automobiles or various types of industrial machines, for example, the plunging constant velocity universal joint, which is designed to permit angular and axial displacement, is employed for the drive shafts of front wheel drive cars or rear wheel drive cars of the independent suspension scheme. One type of plunging constant velocity universal joint is a double-offset constant velocity universal joint. The double-offset constant velocity universal joint mainly includes: an outer race serving as an outer joint member; an inner race serving as an inner joint member; a plurality of balls interposed between the outer race and the inner race to serve as a torque transmitting element for transmission of torque; and a cage for holding all the balls in a plane. The cage has an outer spherical surface in contact with the inner cylindrical peripheral surface of the outer race and an inner spherical surface in contact with the outer spherical peripheral surface of the inner race, in which the center of the outer spherical surface and the center of the inner spherical surface are offset oppositely from each other with respect to the joint center. This is because the joint is of the double offset type. Because the balls are held in one and the same plane by the cage, even at an operation angle, the axial position of the center of the balls is located on a bisecting plane of the outer spherical surface center and the inner spherical surface center of the cage, thereby maintaining the constant velocity property.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2007-71394